lejo

Hi all, i am ready to tack and TIG weld my frame, and i am trying to plan ahead.
My next purcase must be a fork, and for this E-bike / Hybrid / City i am planning on using a fork whithout shocks.
The wheels are 28 inch x 1.75 and i plan on using rim brakes.The headtube is Reynolds 170mm long and 44 mm straight.
This is my first frame build. I don't want to throw $$$ into the fork but i dont want to end up with some crap either.
The ones i have seen which is 1 1/8 straight stem etc is pretty cheap. Most all of them are designed as the pic below.

1. Anyone have any experience with similar forks?
2. Is is possible to use tapered fork in my head tube?

Thanks

Frame

Example fork

guy153

That looks like a decent fork. Some of those generic forks are CrMo, others are some kind of "high tensile" steel (so named because it has a lower tensile strength than CrMo). CrMo obviously a bit nicer. I think you can probably use one with a tapered steerer in that HT but I'm not 100% sure. What I would recommend is to get the fork before tacking the frame so that you can measure it and make sure it's the the length you're expecting. That way if necessary you can tweak your design a bit to match the fork and get the head tube angle you want.

dsaul

The purpose of the 44mm head tube is to be able to run any current fork by choosing the proper headset. You can run a straight 1 1/8", 1 1/2" to1 1/8" tapered, 1 1/4" to 1 1/8" tapered, 1 1/2" straight steerer fork. You just need to choose the proper headset cups to match the crown race and the upper steerer diameter.

One would normally know what fork is to be used in the frame and design the frame using that information, since the axle to crown height of the fork is an important measurement to know for placing the lower end of the head tube. Part of the planning for the frame includes the stack height of the headset, particularly the lower headset stack height, since the external headset cup necessary for a tapered fork will add about 8-10mm of length to the head tube. This extra length on the bottom of the head tube will change all of the angles on the frame, as the front of the frame is lifted and pivots around the rear axle. It probably doesn't matter much on a city bike, but would be a big concern on a more performance oriented bike.

unterhausen

There is one suspension corrected fork that has 1 1/8" steerer and cantilever bosses that everyone seems to sell. You might have more options with disc. I'm not sure that there is a non-suspension corrected fork like that out there, I didn't look.
I second the recommendation of designing around the fork. Production forks don't have much rake and if the head tube angle is too slack then the bike will handle poorly at slow speeds.

I think you need to work on that seat tube/bb miter. That joint is under a lot of stress. I think I have seen more failures there than any other joint.

guy153

The ST/BB mitre might not be as gappy as it looks in the picture. But yes good idea to get it as good as possible. Some other tips for the OP since he said this is frame #1:

1. Triple-check the BB shell is the right way round (lefty-tighty on the right hand side)
2. I would put any bottle cage bosses on now, before attaching the tubes together-- easier to work on them before they're integrated into the frame
3. You may be planning to tack the entire thing and then weld it out. Nothing wrong with this but you can get better access if you do ST to BB first. Then most people do the rest of the front triangle followed by CS and SS last. I do CS and then front triangle. Paul Brodie does DT to BB first.

lejo

Thank you for all the replies. This is really useful! Just to clarify, the ST/BB gap in the picture is not that bad. I haven’t tighten up the Jig. I’ll certainly tripple check BB orientation and i will go over all the miters again. I do have the measurements for the fork as per design. Is it the CC from axle mount to crown which is most important?

I did not know that i could use both tapered and straight stem. Thank you. That gives me alot more options. E.g the Columbus carbon line of forks looks really nice bit the straight stem selection was limited.

I did consider disc brakes but i thought that rim brakes might be more forgiving for a first build so i ended up with that.

dsaul

The important measurement is the axle to crown + the lower stack height of the headset. This determines where the bottom of the head tube is located in the design and on the frame jig.

Devin Rickey

I found this article on Bike Radar to be very helpful while I was learning about the different head tube/steerer options out there: https://www.bikeradar.com/features/t...e-to-headsets/

I am using a 44 mm head tube with a Cane Creek EC44/40 lower and ZS44/28.6 upper to run a tapered steerer suspension fork. The EC lower has a 12 mm stack height.

lejo

Thanks. I have much to learn. I’ll check out the article and hold off for now woth welding until i have fork and bearings verified.

smontanaro 

Apologies for veering off-course, but what is the purpose/advantage of a tapered steerer?

unterhausen

I'm a luddite as far as changing standards like steerers. but tapered steering provide better braking stability, stiffness, and bearing life. This is pretty important for mtb, which currently is stressing bike tech to its limits. OTOH, for a road bike with rim brakes, 1" is fine. Debatable for disc brakes.

https://www.google.com/search?q=what...apered+steerer

lejo

So, finding a fork was not that easy as i thought. Alot of webshops in Norway and UK but either they don't list the measurements or they are way off what i need. I guss the HT length could be shorter and that could make things easier. I don't know. Frustrating either way. Per my design i need a axel to crown length somewhere in the neigbourhood of 378mm and a stem dia of 1 1/8 inch for my 170mm long HT with ID 44mm. The wheel axel is 100mm/9mm and a 28inch/700cc x 1.75. Rake should be around 50mm. Does anyone have some tip for a good supplier? I live in Norway. Have checked out Ceeway and he Colombus catalog but nothing seems to fit there either due to wheel width and rim brake. Sorry for putting this out there but i am a bit shocked by the poor tech info on most webshops :-)

guy153

You could try SJS cycles:

https://www.sjscycles.co.uk/thorn-re...forks-current/

I suspect most unicrown forks of that style will be a bit longer than 380 as a road-fork is usually around 370 or 375. But you can easily make the HT a bit shorter if you need to (although will need to redo some other mitres and perhaps make the whole frame a bit shorter).

Also with such a wide HT you could probably use a "zero stack" headset. Your design may be assuming 12mm which is fairly standard. That would be like having a fork that was 12mm shorter.

If your fork is a bit long it just makes the head angle a bit slacker which probably isn't a huge problem anyway (and it raises the BB a little). 10mm too long or so makes very little difference.

Andrew R Stewart 

The issues the OP is suffering with would be eliminated if they had the parts on hand before any serious designs were started. This goes for components beyond the fork, especially like brakes and wheels these days. Can you say "cart before the horse"?

The classic solution is to make your own fork. I have read comments, over the years, from far more experienced builders then any of us here are about using off the shelf forks VS making them. IMO the only reason to not make your forks is because you want some "quality" that you can't make/work with, like suspension or carbon. Andy

guy153

I didn't make the fork on my first build for safety reasons. Yes a weld is a weld and you should know if you made a complete ballsup of it but all the same, I felt a bit nervous for the first few rides on my first frame, just in case. You never know. I now love making forks and only don't make them if they're carbon or suspension (actually might be fun to make some kind of linkage suspension fork).

bulgie 

@unterhausen answered this well, but I'd just like to add the lightweight factor and the standardization factor, resulting in parts availability.

It's been stated that tapered steerers are better for strength and braking, but not really, compared to untapered that's the same diameter on the top as the larger bottom end of the tapered steerer. For example a steerer that was 1-1/2" untapered would be just as good as a 1-1/8" to 1-1/2" tapered. But it would be heavier for no good reason, and it would need a custom stem. You only need the extra meat at the bottom, so tapered puts it just there. OK that example isn't real-world, but compare straight 1-1/8" steerers to one that's tapered, 1" at the top, 1-1/8" bottom. That would be a sensible steerer, but no stronger than the straight 1-1/8", just lighter. Remember, with the tapered steerer, the stem, headset and part of the head tube can be made lighter too.

Back in the '50s (maybe earlier), both Herse and Singer made tandems with the then-common 28 mm "OS" steerer. But those are unnecessarily heavy up top, so they tapered them on a lathe to be 25 mm up top, to take a standard French upper headset. This required a flared head tube to take the OS lower cup. I always admired that, since I first saw in in the '70s. But never made one myself, mostly because, even by the '70s, the availability of quality 28 mm headset parts was poor. But after the modern 1-1/8" steerer was invented, Seattle framebuilder Dennis Bushnell updated the idea and made tapered 1" to 1-1/8" steerers for tandems, with a headtube he flared himself. Almost the same sizes as Singer's 25 mm to 28 mm, but with easily available modern parts — brilliant. I don't know why that didn't catch on. Other than maybe downhill bikes, 1-1/8" seems unnecessarily heavy up top, so tapered (1" up top) would be better for most bikes that currently use straight 1-1/8". Only a little lighter, but crazier things have been done to save a few grams... And no real downside.

The 1-1/2" steerer was invented pretty much just for plastic bikes, to let the fibers flow from blades to steerer without such a bottleneck at the bottom headset race. But in steel I believe it's way stiffer/stronger than anyone needs. Even MTB forks would be fine with say a 1-1/4" steerer at the bottom, which was a standard for a while but it died out. But the industry has spoken, so now us steel guys are stuck with a standard that only makes sense in plastic. Oh well, we're all dinosaurs, who cares?

Don't get me started! Oops too late.
Mark B

unterhausen

There is a slow motion video of a guy doing bunny hops with a 1 1/8" steerer and that fork flexes like crazy, apparently in the steerer. Current practice with MTB involves a lot of jumping and landing from heights, so I think they need a tapered steerer. Someone that rides like an old person (like me) probably doesn't, but it can't hurt. Usually when I huck to flat it's by mistake.

Doug Fattic 

Lejo, the area where I think you might be surprised to run into unexpected difficulty is your rear triangle putting your rear wheel in the dead center of the plane of your frame (exactly between the chain stays and seat stays). I would be willing to bet a great deal of money that if you tig your chain and seat stays to your vertical rear dropouts using only your fixture to hold them in place, there is almost no chance your rear wheel will center. This is why horizontal dropouts were used in the classic era before those old builders were able to buy or make a decent fixture. The dropout screws adjusted the wheel to fix the issue. I don't trust my very expensive fixtures to do that. Keep in mind that a one millimeter difference in either stay length is magnified about 3 times out by the tire. This is why extra care has to be used or, as an alternative, choose much more forgiving horizontal dropouts.

Most builders (if they are using vertical dropouts) use a "builders wheel" before brazing everything up to insure the lengths are right. This is a wheel that is trued and dished very carefully for intermediate checks.

lejo

Hi all and thank you for giving me very useful input.
I did find a fork thay will fit my design. It is 390 from axle to crown which is ok. I’ll get som zero stack press in bearings. The produser is SLC.

I’ll probably order up a couple of dropouts that are easier to work with.

I have put in alot of time lining up my jig with laser and what not. Have made dummy axle etc but i do see the challenge in getting the rear triangle 100% acurate.

I appreciate that you are taking time to help an amature. I’ll drop in a picture and a progress report when the frame is welded and wheels are on.

Happy Holidays to all!

guy153

Yes this is excellent advice. I recommend:

1. Tack the CS
2. Put a wheel in. Use a known good wheel but also try it both ways around.
3. Weld the CS completely
4. Check again
5. Put the SS in.

Before the SS have gone in it's really easy to bend one CS up a bit and the other down by hand, if necessary, even if they have been welded completely. When checking you can eyeball that the wheel is centered between the CS, but since there are no SS, I wrap a bit of string around the top of the ST/TT junction and assess the top of the rim relative to that. It's harder to eyeball gaps when they're bigger so measure distance from rim to string on both sides.

Also never mind what's in the jig, the two CS should match exactly when you take them out and hold them side by side. Unless the dropouts aren't the same (one has a disk mount or something) in which case this test is not possible.

I actually also tend to only tack the dropouts and only weld those out fully right at the end, when CS and SS are fully attached, just in case, because then I have a last-minute option. But I have never needed this and so just weld them in. Fortunately they don't seem to move.

If it's still not quite right at the end you can file the dropouts a bit which is OK on a first frame but you shouldn't need to do this (and won't have the option if you ever make a thru-axle frame).